Using Ready Boost to Compensate for a Slow Hard Disk

ReadyBoost uses external memory devices (such as USB 2 . 0 flash drives and Secure Digital cards) to cache disk content of all kinds, reducing the need for time-consuming hard disk access. This is yet another feature introduced in Windows Vista that has been significantly improved for Windows 7 . Noteworthy changes include support for concurrent use of multiple flash devices and for caches larger than 4 GB. ReadyBoost supports the exFAT, FAT32, and NTFS file systems .

ReadyBoost technology takes advantage of the fact that flash memory typically offers lower seek times than do hard disks with rotating magnetic media. That fact means your system can get to a given location on a flash drive more quickly than it can to a corresponding spot on a hard disk. Hard disks are generally faster for large sequential reads; flash drives can be quicker for small, random reads. When a supported external memory device is available, ReadyBoost caches data and program code in flash memory and is able to retrieve small chunks of that memory, when needed, more quickly than it could if it relied only on the hard disk


Do you really need ReadyBoost?

Although it got a lot of favorable press when it debuted with Windows Vista a few years ago, ReadyBoost never quite lived up to its promise. And with steady improvements in hardware design since that time, it's become even more of a specialized tool. On a modern, full-sized notebook or desktop PC that was designed to run Windows 7, chances are you'll see little or no improvement by using ReadyBoost. The scenarios in which this technology is most likely to be helpful involve a combination of bottlenecks: limited RAM and a slow hard disk, possibly combined with a low-power CPU. That combination is most likely to be found on small, portable devices popularly known as netbooks. Adding a flash drive of 2 GB or more and dedicating it to ReadyBoost might show noticeable performance improvements in that scenario.

With a fast hard drive and sufficient RAM for caching, you're unlikely to notice any benefit from ReadyBoost. In fact, if you have Windows 7 installed on a fast solid-state disk (SSD), ReadyBoost, SuperFetch, and boot prefetching are all disabled . None of those tools will offer a performance boost in that configuration.

Because an external memory device can be stolen by an attacker with nefarious intentions, and because it can be removed without warning to the system, all data cached via Ready-Boost is encrypted and backed up on the hard disk (as well as being compressed). Encryption ensures that the data can't be read on another system, and backup enables Windows to revert to the hard disk cache in the event that the ReadyBoost drive is removed .

Windows supports the following form factors for ReadyBoost:

• CompactFlash cards

When you connect a device of one of these types to your system, Windows runs a quick performance test to see if the device meets minimum standards required for ReadyBoost. Those standards are

• 2 .5 MB/second throughput for 4-KB random reads

• 1 . 75 MB/second throughput for 512-KB random writes

In addition, the device must have at least 256 MB available for the ReadyBoost cache.


ReadyBoost does not support external card readers . If Windows Explorer shows a volume letter for a drive without media (as it does, for example, for card-reader drives or floppy drives), inserting flash media for that volume letter will not give you a Ready-Boost drive

Windows 7, unlike Windows Vista, supports multiple ReadyBoost drives. If you add two 4-GB USB flash drives to a system, you can combine them to create a single 8-GB Ready-Boost cache .

To use ReadyBoost, first plug a suitable external memory device into your computer. If an AutoPlay window offers the Speed Up My System Using Windows ReadyBoost option, click it. If no AutoPlay dialog box appears, right-click the device icon in the Computer window and click the ReadyBoost tab .

When you inserted the device, Windows ran several brief performance tests to determine whether the device was ready for ReadyBoost. If any of these tests fail, the drive is rejected and you see a red X and a message telling you that the device "does not have the required performance characteristics ." If you think the result is in error, click Test Again to rerun the performance benchmark. A device that passes the test will show a dialog box like the one in Figure 20-8 .

At this point, you have two choices:

• If you want all available storage on the flash device to be used for a ReadyBoost cache, select Dedicate This Device To ReadyBoost. This option is appropriate if the USB drive is meant to be a long-term fixture on a desktop computer.

• If you want to reserve some space on the drive for data files, select Use This Device, and then adjust the slider to specify the amount of space you want to use for Ready-Boost. Then click OK. This option is most useful for scenarios where you're traveling with a large (4 GB or more) flash drive and you only need 2 GB or so to get the most from ReadyBoost.

Microsoft estimates that you can benefit from a ReadyBoost cache equal to at least as much as your system RAM and as much as three times physical RAM—so, for example, a Ready-Boost cache of 1-3 GB is appropriate on a 1-GB system .

Figure 20-8 If you see this dialog box, your device passed the ReadyBoost performance test and is available for use as a supplemental cache.

Figure 20-8 If you see this dialog box, your device passed the ReadyBoost performance test and is available for use as a supplemental cache.

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